Pianoforte



' Oct. 30, 1962 YOSHIO FUKUYAMA PIANOFORTE Filed Oct. 22, 1959 N 9 4 a n H 2 w 7- 1 2 PR PW w N HO. a wm PM 9 FE rm WE JP 5 WHOM (6 F 3 W0" 9. .hQw mm (6 nil. 1 .1%. n n m a .15 INVENTOR YOSH/O Fu/(u Y4M4 WXM ATTORNEYS United States Patent 3,060,783 PIANOFORTE Yoshro Fukuyama, 66 Akasaka Sinzakamati, Minato-ku, Tokyo, Japan Filed Oct. 22, 1959, Ser. No. 848,103 Claims priority, application Japan Apr. 8, 1959 9 Claims. (Cl. 84-194) The present invention relates to a pianoforte or the like, and more particularly to such an instrument equipped with resonance boxes.

The main sound source of a pianoforte are the strings set in vibration, but the sound transmitted from the pianoforte to space comes mainly from the sound-board. Inasmuch as the mode of vibration of the sound-board is complicated just as a frame of a violin or other stringinstrument, the waveform of the sound emitted from a pianoforte is, although of nearly a saw-tooth form, complex, and the sound contains overtones or harmonics ranging up to a very high order. Generally a very high order harmonic is not in consonance with the fundamental tone and therefore deteriorates the tone quality of the musical instrument. Accordingly, it is desirable in a musical instrument to suppress such high order harmonics. However, it is impossible to suppress the high order harmonics by simple mechanical means because of the construction of such instrument. Furthermore, it is very difiicult to faithfully pick up the sound of a pianoforte by a micro-phone even though it is very frequently played on a stage, a radio broadcasting or television studio.

It is, therefore, an object of this invention to minimize the above-mentioned disadvantages of a pianoforte or the like. Indeed, a pianoforte or the like modified in accordance with this invention has beautiful or superior tone quality and increased volume. In addition, the sound of the pianoforte of this invention is faithfully picked up by a microphone.

According to this invention, a pianoforte or the like is equipped with a series of resonance boxes. The resonance frequency of each box in the series corresponds to the resonant frequency of a string in a group, preferably in the middle register of the keyboard of the pianoforte. The series of the resonance boxes is disposed substantially parallel to the sound-board, or similar part of like equipment, inwardly around the periphery thereof, leaving a small distance between the series of resonance boxes and the sound-board. In some cases, this distance may be varied in accordance with the frequency of the resonance box, with a view to obtaining preferable tone quality for sounds of specific pitches. The resonance box comprises a first Wall which is substantially parallel to the sound-board and a second wall substantially perpendicular to the sound board and open to the air outside and provided with one or more holes. Additional holes may be provided in the other box walls if required for fine tuning. The effective opening of the hole may be adjusted by a compensation plate. The function of the series of resonance boxes is to weaken the intensity of the higher order harmonics of the sound of the pianoforte.

The above-mentioned and other features and objects of this invention and the manner of attaining them will become more apparent and the invention itself will be best understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a partial top view of a pianoforte embodying the present invention, With parts above the supports around the edge of the sound-board being removed;

FIG. 2 is an expanded cross-sectional view taken approximately on the line 22 of FIG 1, together with a portion of the supports; and

ice

FIG. 3 is an enlarged view of the left end portion of FIG. 2, showing compensation plates.

Referring to FIG. 1, a portion of a pianoforte 1 embodying the present invention is shown, with a part of the outer case 2 and parts of braces 3 and 3'. As regards the braces 3 and 3', cross-sections shown in FIGS. 2 and 3 are taken slightly in front of and behind the line 22 in FIG. 1, respectively. Referring now to FIGS. 1 and 3 inclusive, a series of resonance boxes designated generally by 4 is disposed under the sound-board (FIG. 3) and strings at a small distance therefrom, beneath and in direct contact with the supports 2 around the edge of the sound-board, along back lower end portion 5 of the case 2, at the level of the braces 3 and 3. In the embodiment shown, some of the braces 3 extend into the series of the resonance boxes 4. One of the braces 3 and a brace 3' or the master cross-brace confine the ends of the series of boxes.

The series of the resonance boxes 4 consists of individual resonance boxes 6 disposed in direct contact with one another and in a row extending along a portion of the case 2. An upper portion 7, bottom portion 8, and front portion 9 are common to a plurality of the resonance boxes 6. These portions are arranged so as to form the upper, the bottom, and the front Wall of the resonance boxes 6, respectively. The case 2 acts as the back wall of the resonance boxes 6. The side walls of the resonance boxes 6 are, in general, formed with partition por- *tions 16 between adjacent resonance boxes. The partition portion 10 of the resonance box adjacent the brace 3 or 3 is replaced by a part of the bracing 3 or 3 itself, while that of the resonance box 6 at an end of the series of the resonance boxes may be replaced by a part of the case 2 itself. In the embodiment shown, it is seen that the resonance boxes 6 are successively arranged in an array.

There are formed in the upper portion and the front portion 9 one or more holes 11 and 12, respectively, per individual resonance box 6. Adjacent each hole 12 is preferably attached a compensation plate 13.

In the embodiment shown, the series of the resonance boxes 4 is composed of twenty-four resonance boxes 6 6 6 the resonance box 6, (i=1, 2, 24) being constructed so as to possess a resonant frequency approximately equal to c, cii, d, b, c, b" (C C D B C B (0 cis d ['1 C2, I12), ((10 (3031i, r63, Sl3, (104, Sl4) of equal temperament of an octave. A resonance box 6 of desired resonant frequency may be designed to some extent by theoretical calculation. The shape and dimensions, however, are determined empirically. In determining the dimensional characteristics of the boxes, it is unnecessary to couple each resonance box 6 with the pianoforte. The designing of the resonance boxes 6 can be determined by making a model of each resonance box 6 having adjustable side walls. The resonance frequency of the box may then be varied by adjusting the walls while sounding a tuning fork or blowing a standard pitch whistleadjacent the model. Once the shapeand the dimensions of each resonance box 6 is determined, it is possible to use the design for all the pianofortes of the same type, because the shape of the case 2 and the position of the braces 3 and 3 are identical.

Fine adjustment or tuning of the resonant frequency of each resonance box 6 may be effected by means of the adjustable compensation plate or plates 13. Fine tuning may also be accomplished by means of a tuning fork or standard pitch whistle in preference to sounding the note on the piano keyboard. The frequency adjustment of the boxes 6 is therefore independent of the piano strings which may be detuned.

The compensation plate 13 which is not shown in FIGS.

1 and 2, is formed, as shown in FIG. 3, of a thin plate 14 which has a sufficient width to cover the hole 12 in the front plate 9, there being one plate per hole. The plates are slidable with respect to the hole 12 by means of slots 15 formed therein and screws 16 which fit into the slots and screwed into the bottom plate 8. At the top end of the thin plate 14 a recess 17 which is of semicircular form and of the same diameter as the hole 13 is preferably formed so that the periphery of the recess 17 may coincide with the lower half periphery of the hole 12 when the compensation plate 1.3 is in a lowered position. In the embodiment shown, the diameter of the holes 11 and 12 are 22 mm. for holes of wide resonance boxes 6 and 18 mm. for holes of narrower resonance boxes 6 and 6 respectively.

Inasmuch as each resonance box 6 has one or more holes in its upper portion 7 and in its front portion 9, the mode of the vibration of the air column in the resonance box is open pipe mode and not closed pipe mode. Open pipe mode of vibration is preferred because of the underside construction of the pianoforte. In the embodiment shown, it will be noted that the resonance boxes 6 6 and 6 are not provided with holes 12 and are of closed pipe form because of the limited width of their front portion but they may be equipped with holes in their bottom portion 8. It is well known that the resonance of an air pipe, irrespective of the types of the pipe, is somewhat different from the theoretical value and requires so-called open end correction. The compensation plate or plates 13 perform this open end correction.

It has been found that the most desirable sound effects are obtained when the resonance frequency of each resonance box 6 is made slightly different from the resonance frequency of the corresponding string of the pianoforte by two or three cycles per thousand.

In a pianoforte, or the like, the vibration of a string is transmitted in the usual manner therefrom to the soundboard. A portion of the sound energy is transmitted in turn from the sound-board into space and the remainder into the resonance boxes 6 to cause resonance in such resonance boxes 6 that are attuned to the fundamental tone or harmonic of the sound created by the vibrating string. Thus, if c (C (do key is touched, resonance boxes 6 which are resonant respectively at c, g, and 0 (C G and C (0 g and c (do S013, and do.;) will resonate. Thus resonating, the resonance boxes 6 emit sounds of which the higher order harmonics are suppressed. It will, therefore, be appreciated that the sound of such a pianoforte will contain far less higher order harmonics, giving beautiful tone as compared with those of conventional construction. In addition, the sound volume of such a pianoforte is louder by virtue of the nature of the resonance box. Thus, it has been found that even with a small pianoforte wherein this invention is embodied, one can produce music having beautiful tone and with sound volume which is comparable to that of a conventional larger instrument. It has furthermore been noticed that the sound of the pianoforte utilizing this invention is picked up more faithfully by a microphone.

There have previously been made various studies of sound-boards and/ or strings of a pianoforte, particularly relative to the mode of vibration and the direction of sound transmission. It has been found that in a grand piano best sound effects are obtainable when the series of resonances boxes 4 is arranged in a manner shown in FIGS. 1 and 2, namely, when the resonance boxes 6 for lower tones are disposed along the back of the pianoforte 1 and each of them being provided with a plurality of holes 11 and 12. The resonance boxes 6 for higher tones are disposed along the right back portion of the case 2. The range of the tones, namely the scope ranging approximately from c to b" (from C to B (from c to W) (from to si is so chosen because the musical sound in this range is more significant; i.e., the melody is usually played in this range. The range may, however, be chosen narrower and it has been ascertained that even with fewer resonance boxes 6 than the number illustrated superior tone quality is obtainable. The resonance boxes 6, once tuned, need not be re-tuned as they will retain their frequency response. They will also aid the piano tuner as he adjusts the tension on the corresponding piano strings. When he tensions a string to resonate exactly at the frequency of the corresponding resonance box 6, the tone will improve due to the attenuation of the unwanted higher order harmonics and he will know that the tuning of that particular string is completed. Inasmuch as the resonance box 6 has equal height to the braces 3 and 3" and is disposed at the same level therewith, the height of the case 2 is the same as that of the conventional one.

While the principles of this invention have been described above in connection with a specifc embodiment, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of this invention.

What is claimed is:

1. A pianoforte, or like instrument, of the type havmg a sound-board adapted to resonate tones made by the sound-producing elements of said instrument, comprising a series of resonance boxes disposed along a peripheral edge of said instrument substantially parallel to said sound-board and spaced therefrom at a given distance, each of said resonance boxes having a resonant frequency approximately equal to the frequency of a corresponding sound-producing element, said resonance boxes being provided for the middle tonal range of said instrument and having dimensions selected so that the response characteristics attenuate higher order harmonics.

2. An instrument according to claim 1, wherein each of said resonance boxes is dimensioned to resonate at a frequency slightly off-set from the fundamental frequency produced by said corresponding sound-producing element.

3. An instrument according to claim 2, wherein said instrument further comprises an outer case supporting said sound-board, said boxes having front, back, top, bottom, and side wall portions, the back wall portion of each box being formed by a portion of said case.

4. An instrument according to claim 3, wherein said top and bottom Wall portions are common to all of said resonance boxes.

5. An instrument according to claim 4, wherein said side walls comprise a plurality of partition elements dividing said top and bottom walls into boxes.

6. An instrument according to claim 3 and further comprising a plurality of spaced braces adapted to support said sound-board Within said case, said series of resonance boxes being arranged in the plane of said braces whereby said braces extend into said series of boxes and constitute a partition Wall between given adjacent boxes of said series.

7. An instrument according to claim 3, wherein said top wall is substantially parallel to said sound-board and adjacent thereto, and said front wall is substantially perpendicular to said sound-board.

8. An instrument according to claim 7, wherein both said top and front walls are provided with apertures.

9. An instrument according to claim 8, and further comprising a plurality of movable plates, each adjacent an aperture of a different one of said boxes, said plates adapted to alter the effective opening of the associated aperture.

References Cited in the tile of this patent UNITED STATES PATENTS 

